ANALYSIS OF DIALLEL CROSSES AMONG COLOMBIAN LANDRACES AND IMPROVED POPULATIONS OF MAIZE

Few of the world's maize (Zea mays L.) germplasm collections have been systematically evaluated in spite of the recognized necessity of broa dening the germplasm base of this crop. Knowledge of new heterotic pat terns and the breeding potential of maize collections stored in gene b anks can contribute to a widening of the genetic base. The objectives of this study were to (i) evaluate the breeding potential of eight tro pical maize germplasms, and (ii) provide further information to clarif y the relationships among them. Five Colombian landraces ('Andaqui', ' Comun', 'Costeno', 'Puya', and 'Yucatan') and three improved maize pop ulations ('Tuxpeno-1', 'Suwan-1', and 'ETO') were crossed in a diallel mating system. The parents and the 28 hybrids were evaluated in six e nvironments for grain yield, days to 50% silking, prolificacy, and ear height. Cultivar (additive) and heterotic effects were highly signifi cant (P less than or equal to 0.01) for all traits except ear height. Significant (P less than or equal to 0.05) cultivar heterosis and spec ific heterotic effects were found for grain yield, with an average 10% high-parent heterosis. Cultivar effects were positive for Suwan-1 (0. 86*) and Tuxpeno-1 (0.62**) and negative for Andaqui (-0.42*) and Puy a (-0.78*). The same materials showed significant cultivar heterotic effects (0.29*, 0.12*, -0.23**, and -0.22**, respectively). Specific heterosis was found in crosses between Tuxpeno-1 and Comun (0.44*), Y ucatan (0.35), and Suwan-1 (-0.67**). The best materials were improve d populations, Suwan-1, and Tuxpeno-1. The ETO population did not perf orm well per se or in hybrid combinations. Yucatan outyielded ETO and was a parent in two of the three highest yielding crosses. The hybrid Tuxpeno-1 x Yucatan showed the highest high-parent heterosis value (25 %*). Results generally agreed with the reported relationships among t he parents and pointed to Yucatan as a potentially useful genetic reso urce for tropical maize breeding programs.